The most important elements in microalloyed steels are niobium and vanadium. Nb is used in low carbon steels known as HSLA (High Strength and Low Alloy) steels. V is used in HSLA steels as well as in medium and high-carbon steels. Compared to Nb, the advantage of V is the very low solubility temperature of carbides, so the nanoprecipitates are usually vanadium nitrides. However, Nb cannot be used in medium and high-carbon microalloyed steels because the solubility temperature of niobium carbides and carbonitrides is very high and these precipitates do not dissolve at reheating temperatures prior to thermomechanical treatment. In this work, an analysis of V nanoprecipitates in thermomechanically-processed steels is carried out by means of scanning and transmission electron microscopy. It is shown that these particles have a mean size of a few nanometers (< 30 nm) due to their low solubility temperature. In consequence, and according to Orowan equation, VN precipitates cause a more remarkable increase in yield strength than NbCN precipitates. Another benefit of V microalloyed steels introduced in this work is the intragranular nucleation of ferrite and bainite in austenite grains existing before phase transformation. VN particles have low interfacial energy with respect to ferrite but relatively high interfacial energy with respect to austenite for the (001)VN boundary compared with other particles or inclusions. Such advantages promote the intragranular nucleation of ferrite and bainite. This work shows that V is an essential alloying element in high strength (> 1000 MPa) microalloyed steels with a ferrite-pearlite microstructure, as well as in bainitic steels. In low carbon steels, with ultimate strength near 600-700 MPa, Nb is also very interesting as a microalloying element. It is used in lower amounts, due to its higher solubility temperature and consequently its higher norecrystallization temperature, which allows a more severe strengthening of austenite and a higher increase in dislocation density. Nevertheless, the intragranular nucleation of ferrite and bainite in V microalloyed steels make this element the best choice, provided that optimal additions are applied. Results about the static recrystallization of austenite during hot rolling and the recrystallization-precipitation-time-temperature (RPTT) diagrams will be also presented in this work. RPTT diagrams display interesting results about the minimum time for precipitation, the recrystallized volume fraction that favors precipitation and the optimal rolling conditions to obtain a very fine ferritic grain size. On the other hand, the increase in yield strength in high strength steels due to the presence of VN precipitates and the improvement in toughness in bainitic steels will be shown. An optimal V/N/Mn ratio will be established. The amount of V used in microalloyed steels is usually between 0.10 and 0.20 %, which means there is an important industrial market for this element. © 2012 by Nova Science Publishers, Inc. All rights reserved.